Okay, this is perhaps stating the obvious, but recently, facebook seems to be making such a bewildering set of changes which trample your privacy, that it's impossible to keep track of what's going on. Take FB messages -- without any notification that I was aware of, it started telling people whether I'd read their messages or not. Then it stopped doing this (as far as I can tell), but kept doing it for group messages. Then it started telling me where people were located when they were messaging me. Incredible!